box-sizing
content-box
Content box height: 280px Total height: 320px = 280px + (2 * 10px) + (2 * 10px) Content box width: 280px Total width: 320px = 280px + (2 * 10px) + (2 * 10px)
border-box
Total height: 280px Content box height: 240px = 280px - (2 * 10px) - (2 * 10px) Total width: 280px Content box width: 240px = 280px - (2 * 10px) - (2 * 10px)